Genetics of carbohydrate metabolism and growth in Eisenia foetida (Oligochaeta: Lumbricidae)

Abstract

The heterozygosity of 13 polymorphic loci, encoding 10 enzymes from several pathways in carbohydrate metabolism, was tested for its effect on growth in juvenile manure worms Eisenia foetida (n = 169), raised under stressful (limited food, low moisture) followed by non-stressful (abundant food, high moisture) conditions. The predictive value of heterozygosity on growth was greatly improved by treating each locus separately rather than summing heterozygosity across all loci (multilocus heterozygosity). Under non-stressful conditions, heterozygosity among loci treated separately had no effect on growth rate (F = 1.60; df = 13, 155; NS); whereas under stressful conditions, heterozygosity among loci treated separately had significant and differential effects on growth rate (F = 234; df = 13, 155; P <0.01) with 7 loci contributing to a positive heterozygosity-growth rate correlation (r =0235; P <0.005) and 6 loci contributing to a negative heterozygosity-growth rate correlation (r = -0•202, P <0.01). Implicated loci could not be easily grouped into specific metabolic pathways. The negative contribution by some loci may arise as a consequence of heterozygote inferiority, linkage disequilibria with positively-contributing loci, or strong selection at that locus.

Correlation between the individual heterozygosity of parents and their offspring

“…This general expectation has provided the incentive for numerous empirical studies of the relationship between individual heterozygosity, the number of loci from a sample for which an individual is heterozygous (Mitton & Pierce, 1980), and various components of fitness (Zouros et at., 1980;Koehn & Shumway, 1982;Pierce & Mitton, 1982;Garton, 1984;Hawkins et at., 1986Hawkins et at., , 1989Rodhouse et at., 1986;Bush et at., 1987; Danzmann et at., 1987;Diehl, 1988;Koehn et at., 1988;Gajardo & Beardmore, 1989;Ferguson & Drahushchak, 1990;Teska et at., 1990;Mopper et at., 1991;Pecon Slattery et al, 1991). These studies reveal that fitness generally increases with heterozygosity (see reviews by Beardmore, 1983;Mitton & Grant, 1984;Allendorf & Leary, 1986;Ledig, 1986;Zouros & Foltz, 1987;Mitton, 1989Mitton, , 1993.…”

Effect of quantity and quality of environmental stress on multilocus heterozygosity-growth relationships in Eisenia fetida (Annelida: Oligochaeta)

“…For the small worms in treatments 3 and 4, intact worms were homogenized in buffer to which phenylmethylsulfonyl fluoride (0.1 mM) had been added to retard the activity of proteolytic enzymes in the anterior portion of the worm. Homogenates were prepared as in Diehl (1988) were resolved on the Tris-maleate, pH 7.4, buffer system of Selander & Yang (1969). All loci except Aap and Hbd were stained according to Diehi & Williams (1 992a).…”

“…In some studies (e.g. Samollow & Soulé, 1983;Diehl & *Correspondence Koehm, 1985), the case that a stressful environment caused MLH-fitness relationships has been made a posteriori. In other studies (e.g.…”

“…Finally, MLH-fitness relationships have been compared in organisms subjected to stressml vs. nonstressful conditions of various types. These latter studies have included comparisons of stressful vs. nonstressful field conditions (Green et al, 1983;Pecon Slattery et at., 1991), comparisons of stressful field vs. nonstressful laboratory conditions (Koehn et a!., 1988), and comparisons of stressful vs. nonstressful laboratory conditions (Koehn & Shumway, 1982;Diehl, 1988;Gentili & Beaumont, 1988; Scott & Koehn, 1990). Despite great differences in the types of environmental stress studied, MLH was usually correlated with fitness in stressed organisms but not in nonstressed organisms.…”

Ontogenetic change in relative performance of allozyme genotypes influences detection of heterosis in the earthworm Eisenia andrei

“…Similarly, Pecon Slattery et al (1993) reported a significant relationship between heterozygosity and age class in the hard clam Mercenaria mercenaria, but the relationship was not consistent over a 3-year sampling period. Consistency of MLH-fitness relationships has also been lacking from a series of studies on Eisenia andrei (Diehl, 1988;Audo and Diehl, 1995;McElroy et al, 1999;McElroy and Diehl, 2001), although some of this inconsistency disappears when a common set of loci are used (Audo and Diehl, 1995). In the above studies, inbreeding, migration, selective mortality, and ontogenetic effects may have affected heterozygosity-fitness relationships.…”